Comparison · Storage & home · 2 models
Glass or plastic food containers: which to buy for which job — Pyrex Cook & Go against Sistema KLIP IT PLUS
Three 0.8-litre glass lunch boxes at nearly half a kilo each, or three 1-litre plastic ones at 123 grams. One goes from freezer to oven; the other must never be cooked in. One is guaranteed for ten years; the other for one. Both go in the microwave with the lid loose and the dishwasher on the top rack. Which to buy depends on what happens to the box after lunch.
Quick answer
Side by side
| Model | Guarantee | Weight per box | Capacity per box | Material | Oven | Microwave | Where to buy |
|---|---|---|---|---|---|---|---|
| Pyrex Cook & Go glass lunch boxes, 3 × 0.8 Lglass — cook, store, reheat and serve in one box | 10 years | 0.48 kg | 0.8 L | Tempered borosilicate glass; BPA-free plastic lid with removable seal | Yes, without the lid; not on a hob | Yes, with the lid unlocked | View listing |
| Sistema KLIP IT PLUS 1 L containers, pack of 3plastic — light, cheap to replace, reheating only | 1 years | 0.12 kg | 1 L | Plastic (type not stated); BPA-free per Sistema's site copy | No — not for cooking, grills or hobs | Yes, without the lid | View listing |
Scroll sideways to see every column
All rules are the makers’ own, from pyrex.co.uk and sistemaplastics.com. Pyrex’s page gives two maximum temperatures (350 and 300 °C) and we record that as a conflict; it does not change any of the advice here.
Weight: the number that decides lunchboxes
glass — cook, store, reheat and serve in one box
Pyrex Cook & Go glass lunch boxes, 3 × 0.8 L
- Guarantee
- 10 years
- Weight per box
- 0.48 kg
- Capacity per box
- 0.8 L
- Material
- Tempered borosilicate glass; BPA-free plastic lid with removable seal
- Oven
- Yes, without the lid; not on a hob
- Microwave
- Yes, with the lid unlocked
Check price on Amazon.co.uk
A Pyrex Cook & Go box is 0.48 kg empty and 20 × 15 × 5 cm outside. Three in a rucksack is 1.44 kg before you put food in them, which is the weight of a laptop. It is also the reason the glass box is so pleasant at home — it sits flat, does not flex, and feels like crockery because it is.
Strengths
- Oven without the lid, microwave with it unlocked, freezer, dishwasher — one box for the whole cycle
- Borosilicate glass rated for a 240 °C shock; ten-year guarantee
- Removable lid seal you can actually clean
Limitations
- 0.48 kg a box — three in a bag is nearly 1.5 kg before food
- 0.8 L is a lunch, not leftovers for two
- Glass breaks if dropped, and Pyrex's page cannot agree whether the limit is 300 or 350 °C
Good for
- packed lunches reheated at work
- batch cooking straight into the freezer and then the oven
- anyone avoiding plastic against hot food
Look elsewhere if
- children's bags or a commute by bike
- the biggest portions
- anyone who weighs their bag
plastic — light, cheap to replace, reheating only
Sistema KLIP IT PLUS 1 L containers, pack of 3
- Guarantee
- 1 years
- Weight per box
- 0.12 kg
- Capacity per box
- 1 L
- Material
- Plastic (type not stated); BPA-free per Sistema's site copy
- Oven
- No — not for cooking, grills or hobs
- Microwave
- Yes, without the lid
Check price on Amazon.co.uk
A Sistema 1 L box is 123 g. Three of them weigh less than one Pyrex box, and they nest — corner shoulders on the base let the empties stack inside one another. For anything carried daily, that is the argument, and it is not close.
Strengths
- 123 g a box against nearly half a kilo for glass
- Leak-proof flexible seal and clips; nests when empty
- Made in New Zealand, and any Sistema 1 L lid fits
Limitations
- Not for the oven, grill or hob — reheating only
- Sistema does not name the plastic and warns it may stain with tomato or turmeric
- One-year warranty
Good for
- packed lunches carried every day
- children, bikes and bags that get dropped
- batch cooking into identical boxes
Look elsewhere if
- cooking or roasting in the container
- anyone avoiding plastic against hot food
- oven-to-table
Heat: what each is allowed to do
Pyrex: oven without the lid, microwave with the lid unlocked, fridge, freezer, dishwasher; not on a hob. The glass is tempered borosilicate rated for a 240 °C thermal shock under EN 1183 — Pyrex’s own example is freezer at −20 °C straight into a 200 °C oven. The lid is BPA-free plastic with a removable seal, never for the oven.
Sistema: microwave without the lid, for reheating only; dishwasher top rack; freezer with space left for expansion. Not for cooking — no oven, grill, hob or convection microwave. Sistema adds that tomato, beetroot, curry and turmeric may stain the plastic when reheated.
That is the real division. If the box ever goes in an oven, or if you want to cook a batch, portion it into boxes, freeze them and bake one on Thursday, it has to be glass. If the box’s hottest moment is two minutes in a microwave, plastic is allowed everything you will ask of it.
Lids, seals and leaks
Both are clip lids with seals and both makers call them leak-proof. Pyrex’s seal is removable — you can take it out, wash behind it and put it back, which is the hygienic answer to the grey line that forms in fixed seals — and the lid has a space to write the contents. Sistema’s seal is built into the lid, flexible, and paired with the range’s locking clips; it is not removable, and it is the design Sistema has sold for decades. Any Sistema 1 L KLIP IT lid fits any Sistema 1 L box, which matters in a house that loses lids.
Breakage, staining and years
Glass breaks when dropped and plastic does not, which settles the children’s-bag question. Plastic stains and glass does not, which settles the chilli question. Pyrex guarantees the glass for ten years against manufacturing defects (not against being dropped); Sistema guarantees its boxes for one year. Pyrex is made in France; Sistema in New Zealand. Neither maker names the plastic in its lid or box beyond “BPA-free”.
Capacity and shape
The Pyrex is 0.8 litres and shallow — 20 × 15 × 5 cm outside — which is a lunch or a portion, and shallow enough to heat evenly in an oven. The Sistema is a full litre and taller (17.6 × 12.8 × 7.9 cm), which takes a bigger lunch or a portion of leftovers with a sauce. Neither is a batch-cooking size; both makers sell bigger boxes in the same ranges.
Which one, by job
- Meal prep into the freezer, reheated in the oven: Pyrex.
- Oven-to-table, or anyone avoiding plastic against hot food: Pyrex.
- Daily packed lunch, microwaved at work: Sistema, for the weight — or Pyrex if the weight does not bother you.
- Children, bikes, gym bags: Sistema.
- Curries and tomato sauces stored for days: Pyrex, because it will not stain.
- A house that loses lids: Sistema, where every 1 L lid fits every 1 L box.
Sources
Facts checked 24 September 2026
- Pyrex UK (International Cookware) — Cook & Go set of 3 rectangular 0.8 L lunch boxes, ref. 913S219 (page and Shopify product JSON) — Manufacturer documentation, checked 24 September 2026
- Amazon.co.uk listing (Pyrex) — Retailer listing, checked 24 September 2026
- Sistema — KLIP IT PLUS 1 L Rectangle 3-pack, style 881613 — Manufacturer documentation, checked 24 September 2026
- Sistema — KLIP IT PLUS 1 L Rectangle single container, style 881600 (comparison table) — Manufacturer documentation, checked 24 September 2026
- Sistema — FAQs (warranty) — Manufacturer documentation, checked 24 September 2026
- Amazon.co.uk listing (Sistema) — Retailer listing, checked 24 September 2026
Can glass containers go in the oven with the lid on?
No. Pyrex's rule for Cook & Go is oven without the lid; the lid is plastic and is for the fridge, freezer and — unlocked — the microwave. The glass itself is tempered borosilicate rated by Pyrex for a 240 °C thermal shock, so the box can go from a −20 °C freezer into a 200 °C oven, but not onto a hob.
Can plastic containers go in the microwave?
Sistema's rule: microwave without the lid, for reheating only. The containers are not for cooking, and Sistema says not to use them in a conventional oven, under a grill, on a hob or in a convection microwave. Sistema also warns that tomato, beetroot, curry and turmeric may stain them when reheated.
Freezer to oven — which one?
Only glass, and only the right glass: Pyrex rates Cook & Go's borosilicate for a 240 °C difference under EN 1183, which is what freezer-to-oven means. Sistema's plastic is freezer-safe — leave space for expansion — but must never be heated beyond reheating in a microwave.
Which is better for a packed lunch?
Plastic, unless weight does not matter to you. A Pyrex 0.8 L box is 0.48 kg empty; the Sistema 1 L is 0.123 kg — three of each is 1.44 kg against 0.37 kg before any food. Glass wins when the lunch is reheated at work in an oven or you want nothing but glass against hot food; plastic wins on a bike, in a child's bag, and every time a box is dropped.
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